The present invention relates generally to fastening apparatuses and more particularly to a fastening apparatus for forming a clinch joint between sheets of material.
It is common within the metal forming industry to join overlapping workpiece sheets by punching or otherwise deforming them to cause an interlocking relationship in a localized area. Many of these traditional joints, however, have typically required shearing of the sheet material. Thus, these joints tend to leak rain water and also have their corrosion resistant coatings destroyed.
More recently, an apparatus has been used for joining two or more sheets of material together by creating a leakproof and secure joint. These improved conventional joints are created by use of a punch acting against an anvil to produce what is known as a TOG-L-LOC® clinch joint therebetween. Such a leakproof joint and tooling are disclosed in U.S. Pat. Nos. 5,267,383 and 5,177,861, both of which are entitled “Apparatus for Joining Sheet Material” and U.S. Pat. No. 5,727,302, entitled “Die and Punch for Forming a Joint and Method of Making the Die,” all of which issued to Sawdon. The disclosures of these patents are incorporated by reference herein. These conventional leakproof joints have seen commercial success for use in varied applications such as microwave oven home appliances and automotive vehicle parts.
Other traditional die configurations are known. For example, U.S. Patent Publication No. 2004/0045153 entitled “Method and Tool for Producing A Press Joint Connection” shows pairs of spaced apart die segments retained by individual leaf springs and their associated screws. This traditional construction, however, leaves the moving die components fully exposed to the harsh environment of a typical manufacturing plant such that the die segments appear to be susceptible to falling off of the die, and the spring interfaces to the die segments and screws may be worn or deformed over time through inadvertent workpiece contact or die vibration.
In accordance with the present invention, a sheet fastening apparatus and method are provided. In another aspect of the present invention, a single biasing member is configured to retain movable die blades in a die assembly while allowing outward movement of the die blades relative to a central anvil. A further aspect of the present invention provides multiple die blades each having a partially circular punch-side shape at their overlap with an anvil. In yet another aspect of the present invention, a die assembly for forming a joint between sheets of material is disclosed wherein the die assembly includes an anvil, at least one die blade disposed adjacent to and overlapping a punch-side of the anvil, a flexible retainer, and a shield that coaxially and radially surrounds a portion of the anvil and/or die blade. In still another aspect of the present invention, die blades have an interior undercut and the die blades contact each other in at least one operating condition. Methods of making and using a die assembly that is used for forming a joint between at least two sheets of material are also provided.
The present invention is advantageous over prior constructions since the present invention improves joint quality by minimizing overly deep drawing of soft material workpieces, such as aluminum sheets. Thus, joint tearing or cracking is reduced. The present invention is further advantageous since the die assembly is less expensive to manufacture, simple to assemble, and more durable, robust and protected in use than many traditional devices. Moreover, the present invention apparatus advantageously allows joining of three or more material sheets. The apparatus of the present invention is ideally suited for joining together aluminum/polymer/aluminum composite panels used to reduce noise. Additional advantages and features of the present invention will become apparent from the following description and appended claims, taken in conjunction with the accompanying drawings.